Method of making a magnetic core



Nov. 22, 1960 J. c. BENDER ETAL 2,960,755

METHOD OF MAKING A MAGNETIC CORE Filed Dec. 10. 1956 2 Sheets-Sheet 1 (/06/7 C. Bender Cu//e/7 M Vfiww er INVENTORS gw/zm ATTORA/EVJ Nov. 22, 1960 J. c. BENDER ETAL 2,960,755 METHOD OF MAKING A MAGNETIC 'CORE Filed Dec. 10. 1956 2 Sheets-Sheet 2 Cu//6/7 M l Vfiarfer INVENTORS y Mw4% 12M ATTO/WVEYJ United States Patentffice 2,960,755 Patented Nov. 22, 1960 2,960,755 METHOD OF MAKING A MAGNETIC CORE.

John Carlos Bender and Cullen J. McWhorter, Houston, Tex., assignors to Houston Oil Field Material Company, Inc., Houston, Tex., a corporation of Delaware Filed Dec. 10, 1956, Ser. No. 627,324

4 Claims. (Cl. 29155.57)

The present invention relates to a method of making a magnetic core which is used as a core to carry a winding for use, in well bores.

The use of a material, for example, a ferromagnetic material, which has the property of being magnetic and also a good-insulator, is desirable for use as a core to carry the winding of a coil, especially for use in well bores to determine the location of a stuck point of the pipe in they bore'or to locate casing collars as well as other elements in the well bore.

Heretofore, such cores have been formed of extruded ferrite or other term-magnetic material such as that manufactured by the Henry Crowley Company of West Orange, New Jersey, known as Croloy 20, and good results were obtained when these cores were in good condition. Unfortunately, these cores, as well as others, are very fragile, and after being subjected to conditions in a well bore, for example extreme external pressure due to hydrostatic pressure and the like, these cores crack,.

break, have holes and spaces between the coil core and adjacent members and become unsatisfactory for use. In quite a few instances, these cores can be used only for one-or two runs and then must be discarded.

In some coil assemblies, the coil rod 18 screwed directly into the top and bottom subs. In this case, the coillead wire must be brought out through, and insulated-from, the coil rod. This is a disadvantage because the coil rod is weakened and in many cases hydrostatic pressure in the well bore shears the insulation and floods the inside of the coil rod thus rendering it inoperative. Also, inconventional coil assemblies for use in well bores, the extreme hydrostatic pressures encountered shear or break loose vulnerable electrical connections and the coil core cannot successfully withstand the shock, bend.ng,,

torsion and extreme compressive forces to which it is subjected in use.

It would therefore be highly advantageous, audit is an object of this invention to provide a method of .making a corewhich not only serves the function of a core for a coil winding, but is a structural elementv which v.is

rugged and durable and can successfully withstand the shock, bending, torsion and extreme compressive forces to which it is subjected in use.

Still a further object of this invention is the provision of a method of making a core for a coil Winding which has either conductive or non-conductive magnetic and insulating properties which eiiectively withstands conditions ina well bore.

Yet a further objectiof this invention is the provision of a method for making a core having magnetic and insulating properties suitable for a coil winding and capable of extendeduse in a well bore.

It is still a further object of this invention to provide a method of making a coil assembly having its core support rodinsulated from the connectors at each end and in which the support rod is connectedat each end through the medium of insulators in such a manner that thenormal tensile strength of the connecting area.

on the rod is not lessened.

It is yet a further object of. this invention to provide a method ofmakinga coil assembly having a core formed of a tough, hard and strong resin impregnated with magnetic particles.

Still a further object of this invention is the provision of a method of making a coil assembly in which there are no vulnerable electrical connections, and in which the coil lead wire is not brought out through the core support rod.

Other and further objects, features and advantages will be apparent from the following description of a presentlypreferred example of the invention, given for the purpose of disclosure and taken in conjunction with the accompanying drawings, where like character references designate like parts throughout the several views, and where Figure 1 is a side elevation, in section, illustrating a step in making a core according to the invention,

Figure 2 is a view similar to Figure l and illustrates the next step in making a core according to the invention, and

Figure 3 is a side elevation, in section, illustrating a completed core assembly with a winding according to the invention.

Referring now to the drawings, and particularly to Figure 1, a generally tubular core rod support 10 is provided which has the reduced-diameter threaded portions 12 and 14 at each end into which are threaded the insulators 16 and 18, respectively, having the internallythreaded portions 20 and 22, respectively, for this purpose. The insulators 16 and 18 have the externallythreaded pin-type portions 24 and 26 so that the core structure can be threaded to other elements in use. The rod 10 is formed of a material capable of conducting electrical energy and the insulators are formed of nonconducting materials. The passage 11 through the core support rod 10 is for the purpose of permitting additional electrical connections below, for example in detonating an explosive for impacting a connection to assist in its release. The passage 11, of course, may be omitted if desired.

The insulating connectors 16 and 18 are conformed to fit snugly about the ends of the core support 10 and have the outwardly facing shoulders 28 and 30 for smoothly receiving the boxes 29 and 31 of adjacent elements when assembled, see Figure 3. Turning again to Figure 'l,.the inner portion of the connectors 16 and 18 have a diameter portion 32 and 34, respectively, for reception of the sleeve 36 and for providing an annular support 10 thus serving as an electrical connection between the coil and core support rod 10, as will be apparent later. The sleeve 36 is placed about the core support and the bottom connector 16, as shown, with the top connector 18 left off. A magnetic material 38 is then placed between the sleeve 36 and core support rod 10 and above the washer 40 and tamped to avoid open spaces. Sufiicient material is used to avoid any open spaceibetween the washer 40 at the bottom and the top connector .18 when these elements are secured to the core support-10, as shown. The material may be any magnetic material, for example, ferrite or other ferro-magnetic materials and may be in powdered, granular, tubular, rolled or other form. Also, depending upon the frequencies desired, the material may either be conductive or non-conductive. The insulator connector 18 is then screwed onto the threaded portion 14 of the core support 10.

Turning now to Figure 2, resin is injected into the space between the sleeve 36 and core and impregnates the magnetic material 38. Any self-hardening or thermosetting resin which sets or is cured to a strong, tough, hard mass may be used, for example, any of the polyethylene resins. One suitable resin is sold commercially as Epon.

Preferably, the core is inverted and the resin is injected from the bottom, the assembly being held in an inverted vertical position until resin comes out the space between the top of the sleeve 36 and the connector 16. In this manner the liquid resin rises evenly on all sides and carries the air ahead of it thereby avoiding air spaces in the resin when set.

For injecting the resin in this manner, a gun 40 is used which includes the piston 42 movable in the piston cylinder 44 which contains the resin 46. A projection 48 is provided on the cylinder 44 and includes a cylindrical opening 50 which snugly fits about the connector 18 and sleeve 36. An annular opening 52 is provided in communication with the interior of the cylinder 44 so as the piston is moved inwardly, resin is forced evenly into the space between the lower portion of the sleeve 36 and diameter portion 34 of the connector 18. Suitable packing rings 54 are provided on each side of the annular passage 52 for packing ofi this opening.

The gun 40 is satisfactory in use, although any suitable means or manner may be employed for injecting the resin and impregnating the magnetic particles.

When the resin comes out of the space at the top between the reduced diameter portion 32 of the connector 16 and the sleeve 36, injection is stopped and the gun removed. The resin is then allowed to set, or in the case of thermosetting resins is cured by heating.

-After the resin has hardened, the sleeve 36 is removed, and as shown in Figure 3, the assembly is inverted and a coil winding 56 is wound about the resin impregnated with magnetic particles which is designated generally by the reference numeral 58. One end of the coil 56 is connected to the washer 40 thus completing an electrical connection with the core support 10 which has the electrical lead 60 connected thereto, such as by silver soldering, so that electrical energy is provided from the lead 60 through the core support rod 10 to the washer 40 and to the coil 56. A ground ring 62 is provided about the other end of the core support rod 10 and insulator 18 to which the other end of the coil 56 is connected, such as by silver soldering, and is grounded due to its engagement with the sub 31 which is screwed onto the threaded portion 26 of the insulator connector 18. As previously mentioned, a sub 29 is also threaded onto the threaded portion 24 of the insulated connector 16.

In use, if desired, a covering may be placed about the coil 56. It should be noted that the coil and coil core are supported at the thickest portion of the core support 10 and that the threaded sections of the subs 29 and 31 overlap a considerable distance with the threaded ends of the core support rod 10 through the medium of the insulators 16 and 18. The length of the threaded sections 24 and 26 is enough to provide shear strength approximately equal to the tensile strength of the threaded ends 12 and 14 of the core support rod 10.

The finished coil assembly possesses desirable electrical properties and at the same time has sufiicient tensile strength to Withstand shock, bending, torsion and extreme compressive forces encountered in use in well bores. Vulnerable electrical connections have been eliminated so that the coil assembly withstands extreme pressures without failure. The coil core support serves the dual function of being an electrical conductor and a structural member, and a tough, hard and durable coil core is provided which is so closely integrated with adjacent members that a coil Wound about its surface is not subjected to breakage due to external pressure. The coil assembly may thus be used sucessfully in well bores in investigating conditions in well bores, for example, locating casing collars, struck points of pipe and the like.

The present invention therefore is well suited to carry out the objects and attain the ends and advantages mentioned as well as others inherent therein.

While only a presently-preferred example of the invention has been given for the purpose of disclosure, many changes in detail, steps of construction and arrangements of parts may be made which are encompassed within the spirit of the invention and the scope of the appended claims.

What is claimed is:

1. A method of forming a coil assembly comprising, securing a first insulator connector having a stop member to an end of a core support rod capable of serving as an electrical conductor, placing a sleeve concentrically about the core support rod and against the stop member, said sleeve being of a diameter sufficient to form an annular space between the core support rod and the sleeve, inserting particles of magnetic material into the annular space but leaving space for a second insulator connector to extend into said annular space, securing a second insulator connector to the other end of the core support rod, a portion of said second insulator connector extending into and spaced from the sleeve, injecting a resinous material into said annular space about the particles of magnetic material, removing the sleeve, securing a ground sleeve about the second insulator, winding a coil about the impregnated magnetic material, and electrically connecting one end of the coil to the core support rod and the other end of the coil to the ground sleeve.

2. The invention of claim 1 including the step of injecting the resinous material into the space'between the second insulator connector and the sleeve while the second insulator connector is positioned below the first insulator connector whereby the resinous material rises evenly and avoids air space in the impregnated magnetic material.

' 3. A method of forming a coil assembly comprising, securing a first insulator connector to an end of a core support rod capable of serving as an electrical conductor, securing an electrical conducting washer to and about the core support rod adjacent said first insulator connector, placing a sleeve concentrically about the core support rod, said sleeve being of a diameter sufiicient to form an annular space between the core support rod and the sleeve and to fit over and provide a reduced annular space with respect to said first insulator connector, inserting particles of magnetic material into the annular space but leaving space for a second insulator connector to extend into said annular space, securing a second insulator connector to the other end of the core support rod, a portion of said second connector extending into and spaced from said sleeve, injecting a resinous material into said annular space about the particles of magnetic material, removing the sleeve, securing a ground sleeve about the second insulator, winding a coil about the impregnated magnetic material and electrically connecting one end thereof to the washer and the other end thereof to the ground sleeve, and connecting a coil lead wire to the coil support rod.

4. The method of claim 3 wherein the resinous material is injected into the space between the sleeve and the second connector while the second connector is positioned below the first connector whereby the resinous material rises evenly through the particles of magnetic material and prevents air spaces in the impregnated magnetic material.

References Cited in the file of this patent UNITED STATES PATENTS 1,497,469 Ames June 10, 1924 1,978,568 Crossley et al Oct. 30, 1934 2,455,960 Wall Dec. 14, 1948 2,654,142 Horelick Oct. 6, 1953 2,720,693 Charbonneau et al Oct. 18, 1955 A an." 

